The present invention relates generally methods for the detection and diagnosis of cancer in a subject. More particularly, the invention relates to methods and kits for detecting Pgrmc1 (progesterone receptor membrane component 1) in a bodily fluid sample to facilitate the detection and diagnosis of cancer, particularly lung cancer.
Cancer is one of the leading causes of death, and there is an urgent need for new biomarkers and therapeutic targets and method for early detection of cancer. Lung cancer is the leading cause of cancer death worldwide, resulting in 150,000 deaths per year in the United States. The mortality rate from lung cancer is greater than the combined mortality from breast, prostate and colorectal cancers. On the basis of morphology, lung cancer can be broadly classified into four main categories namely, adenocarcinoma, squamous cell carcinoma, large cell undifferentiated carcinoma and small cell carcinoma. Both squamous cell carcinoma and small cell carcinoma are strongly associated with a smoking history.
Adenocarcinoma, squamous cell carcinoma, and large cell undifferentiated carcinoma are usually referred as “non-small cell carcinoma.” They are relatively chemo-resistant, and hence the mainstay of treatment is surgery. By contrast, small cell carcinoma has a higher propensity for distant metastases and is mainly treated by chemotherapy.
While biopsy can be used to diagnose various cancers, it is an invasive procedure and, therefore, less than desirable. Other diagnostic methods for cancers include ultrasound and computed tomography (CT) scan. Nonetheless, methods and kits for detecting biomarkers associated with cancer, particularly biomarkers present in a blood or serum sample, are urgently needed to facilitate early detection and treatment of cancer.
EGFR (epidermal growth factor receptor) is one of the most promising therapeutic targets in lung cancer, and EGFR inhibitors have produced positive clinical results, particularly for patients with activating mutations in the EGFR kinase domain (Gazdar A F., Oncogene 2009,28 Suppl 1:S24-31; Lynch et al., The New England Journal of Medicine 2004; 350:2129-39; Pao et al., Proc Natl Acad Sci USA 2004; 101:13306-11).
Pgrmc1 (progesterone receptor membrane component) is a microsomal protein that colocalizes with EGFR in the endoplasmic reticulum or punctate cytoplasmic sites. Pgrmc1 associates with EGFR in lung cancer cells and increases susceptibility to the EGFR inhibitor erlotinib, it is also a cytochrome b5 related protein. (Hughes et al., Cell Metab 2007; 5:143-9; Ahmed et al., J Biol Chem 2010, 285:24775-82; Crudden, Chitti and Craven R J., J Pharmacol Exp Ther 2006, 316:448-55; Nolte et al., Biochim Biophys Acta 2000; 1543:123-30; Peluso, Romak, and Liu, Endocrinology 2008; 149:534-43; Min et al., FEBS J 2005, 272:5832-43; Mifsud and Bateman, Genome Biol 2002, 3: RESEARCH0068; Cahill, J Steroid Biochem Mol Biol 2007, 105:16-36). Recently, Pgrmc1 was identified as a sigma-2 receptor (S2R), with a clear role in tumor cell survival.
Pgrmc1 is also induced in multiple tumor types. For example, Pgrmc1 is induced in approximately approximately one-half of breast tumors compared to matched nonmalignant tissue, and Pgrmc1 is enriched in estrogen receptor-negative breast tumors (Crudden et al., Tumour Biol 2005, 26:142-6; Neubauer et al., Breast Cancer Res 2008, 10:R85). In ovarian cancer, Pgrmc1 expression increases with tumor stage, and Pgrmc1 is also enriched in colon and lung cancers (Peluso et al., J Clin Endocrinol Metab 2008, 93:1592-9; Letwin et al., Cancer Res 2005 65:1814-21; Irby et al., Cancer Res 2005, 65:1814-21; Difilippantonio et al., Eur J Cancer 2003; 39:1936-47). The mechanism through which Pgrmc1 is induced in tumors is unclear, but may include induction by carcinogenic compounds (Difilippantonio 2003; Selmin et al., Carcinogenesis 1996; 17:2609-15; Nie et al., Mol Carcinog 2006; 45:914-33). Pgrmc1 is inhibited by a small molecule ligand called AG-205, which inhibits growth in tumor cells and decreases EGFR levels (Ahmed et al., J Pharmacol Exp Ther 2010, 333:564-73; Ahmed et al., J Biol Chem 2010, 285:24775-82). Pgrmc1 also contributes to multiple features of tumor growth. In lung adenocarcinoma cells, Pgrmc1 promotes proliferation, anchorage-independent growth, migration, primary tumor growth and metastasis (Ahmed et al., J Pharmacol Exp Ther 2010). Pgrmc1 has a similar biological role in ovarian cancer, where it regulates tumor growth as well as angiogenesis and tumor pathology (Peluso et al., Endocrinology 2009, 150:4846-54). Pgrmc1 also suppresses apoptosis in immortalized granulosa and ovarian cancer cells (Peluso et al., Endocrinology 2006, 147:3133-40; Peluso et al., J Clin Endocrinol Metab 2008, 93:1592-9) and contributes to mitotic progression in ovarian cancer (Lodde et al., Biol Reprod 2010, 84:215-222). Pgrmc1 is inhibited by a small molecule ligand called AG-205, which inhibits growth in tumor cells and decreases EGFR levels (Yoshitani et al., Proteomics 2005, 5:1472-80; Ahmed et al., J Pharmacol Exp Ther 2010; Ahmed et al., J Biol Chem 2010.